Non-linear resistive elements generally called a varistor show a characteristic of a resistance value thereof varying with a voltage applied thereto, i.e., have a non-linear voltage-current characteristic such that the element has a high resistance value showing an insulating characteristic when a normal voltage is applied thereto, while having a low resistance value when an abnormal high voltage is applied thereto. The varistor having such characteristic are broadly utilized in a surge arrester or a surge absorber for the purpose of absorbing surge and noise, or in a voltage stabilizing element.
The non-linear resistive element is, for example, composed of ceramic sintered compact (green body) obtained by molding and sintering zinc oxide powder including a bismuth oxide, antimony oxide, and cobalt oxide as basic additive to develop a non-linear voltage-current characteristic, and various types of oxide added to further increase the performance, which are added to zinc oxide as a primary component, and by sintering the compact.
On a surface and a reverse surface of this ceramic sintered compact, a base conductive layer is formed by a glazing process of silver paste. On this base conductive layer, metal electrode plates composed of a conductor of copper, brass, or aluminum or the like, are plurally joined by soldering. Then, a main portion including the ceramic sintered compact and the electrode plate is molded by epoxy resin or the like, thereby a non-linear resistive element in which a terminal area of an electrode member is derived from the mold part is made into a product. (for example, Patent Document 1).